Such patients, the researchers wrote, often see no connection between their current problems and events that may have happened years before.
The results, the researchers write in the journal Nature, raise questions about the future and the past.
In the past, he said, researchers writing about black student achievement have often been unaware of the work others were doing.
To our knowledge, none are yet being used in patients, the researchers write.
But only two of those patients reported cough improvement, the researchers write.
Several independent researchers have also written critiques of the film.
So researchers must write special computer programs to copy the data onto modern tapes.
Medical researchers, after all, do not write for patients.
Nearly all the increase was in deaths from gunshot, the researchers wrote.
However, "the magnitude of this effect was relatively small," the researchers write.